Brake position system

ABSTRACT

A brake actuator system may comprise a brake actuator comprising a ball screw, a ball nut coupled to the ball screw, and a ram coupled to a ram end of the ball nut; a position sensor coupled to the brake actuator; a processor in electronic communication with the brake actuator and the position sensor; and/or a tangible, non-transitory memory configured to communicate with the processor, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the processor, cause the processor to perform operations. The operations may comprise commanding the brake actuator to translate the ball nut in a first direction toward a brake stack; detecting the ram reaching a furthest forward position; and commanding the brake actuator to translate the ball nut in a second direction opposite the first direction for a total retraction distance.

FIELD

The present disclosure relates to aircraft brake systems and methods,and more particularly, to systems and methods for detection of brakedisc position.

BACKGROUND

Vehicle wheel assemblies (e.g., in aircraft, automobiles, or the like)may comprise brake stacks which stop the vehicle in response to thecompression of rotating and stationary brake discs by either hydraulicor electromechanical actuators. To engage the brakes, a ball nut maytranslate a ram to contact the brake discs to cause the compression ofthe brake discs. When not engaged, the ram may rest in a position thatis resting on or near an adjacent brake disc of the brake stack suchthat the ram is not causing compression of the brake stack.

SUMMARY

In various embodiments, a brake actuator system may comprise a brakeactuator comprising a ball screw, a ball nut coupled to the ball screw,and a ram coupled to a ram end of the ball nut; a position sensorcoupled to the brake actuator; a processor in electronic communicationwith the brake actuator and the position sensor; and/or a tangible,non-transitory memory configured to communicate with the processor, thetangible, non-transitory memory having instructions stored thereon that,in response to execution by the processor, cause the processor toperform operations. The operations may comprise commanding the brakeactuator to translate the ball nut in a first direction toward a brakestack; detecting the ram reaching a furthest forward position; and/orcommanding the brake actuator to translate the ball nut in a seconddirection opposite the first direction for a total retraction distance.In various embodiments, the operations may further comprise determining,by the processor, a running clearance position of the ram in response totranslating the ball nut for the total retraction distance, wherein therunning clearance position may be positioned the total retractiondistance away in the second direction from the furthest forwardposition. In various embodiments, the furthest forward position may bedictated by a maximum current applied to the brake actuator, wherein themaximum current allows the brake actuator to translate the ball nut inthe first direction to the furthest forward position.

In various embodiments, the commanding the brake actuator to translatethe ball nut in a second direction for the total retraction distance maycomprise commanding, by the processor, the brake actuator to translatethe ball nut in the second direction for a predetermined retractiondistance from the furthest forward position; determining, by theprocessor, a zero torque position of the ram in response to translatingthe ball nut for the predetermined retraction distance, wherein the zerotorque position may be positioned the predetermined retraction distanceaway in the second direction from the furthest forward position; and/orcommanding, by the processor, the brake actuator to translate the ballnut in the second direction for a clearance distance from the zerotorque position. The predetermined retraction distance and the clearancedistance may collectively equal the total retraction distance. Invarious embodiments, the brake actuator system may further comprise aposition detection system by which the brake actuator system determinesthe running clearance position, wherein the operations may furthercomprise detecting, by the processor, that the position detection systemis malfunctioning before the commanding the translation of the ball nutin the first direction.

In various embodiments, the detecting the ram reaching a furthestforward position may comprise detecting, by the processor, the brakeactuator stalling in response to the brake actuator receivinginsufficient current to translate the ball nut further in the firstdirection. In various embodiments, the total retraction distance may bemeasured by the position sensor. In various embodiments, the positionsensor may be a resolver. In various embodiments, the operations mayfurther comprise receiving, by the processor, a signal from the resolvercomprising distance information; and determining, by the processor, adistance that the ball nut translated in the first direction from aninitial position to reach the furthest forward position.

In various embodiments, a method may comprise applying a current to abrake actuator comprising a ball screw; commanding, by a processor, thebrake actuator to translate a ball nut coupled to the ball screw in afirst direction toward a brake stack; detecting, by the processor, a ramcoupled to a ram end of the ball nut reaching a furthest forwardposition; and/or commanding, by the processor, the brake actuator totranslate the ball nut in a second direction opposite the firstdirection for a total retraction distance. In various embodiments, themethod may further comprise determining, by the processor, a runningclearance position of the ram in response to translating the ball nutfor the total retraction distance, wherein the running clearanceposition may be positioned the total retraction distance away in thesecond direction from the furthest forward position. In variousembodiments, the method may further comprise detecting, by theprocessor, that the position detection system is malfunctioning beforethe commanding the translation of the ball nut in the first direction.In various embodiments, the method may further comprise receiving, bythe processor, a signal from a position sensor comprising distanceinformation; and determining, by the processor, a distance that the ballnut translated in the first direction from an initial position to reachthe furthest forward position.

In various embodiments, the commanding the brake actuator to translatethe ball nut in a second direction for the total retraction distance maycomprise commanding, by the processor, the brake actuator to translatethe ball nut in the second direction for a predetermined retractiondistance from the furthest forward position; determining, by theprocessor, a zero torque position of the ram in response to translatingthe ball nut for the predetermined retraction distance, wherein the zerotorque position may be positioned the predetermined retraction distanceaway in the second direction from the furthest forward position; and/orcommanding, by the processor, the brake actuator to translate the ballnut in the second direction for a clearance distance from the zerotorque position. The predetermined retraction distance and the clearancedistance may collectively equal the total retraction distance.

In various embodiments, detecting the ram reaching a furthest forwardposition may comprise detecting, by the processor, the brake actuatorstalling in response to the brake actuator receiving insufficientcurrent to translate the ball nut further in the first direction. Invarious embodiments, the position sensor may be a resolver. In variousembodiments, the applying the current to the brake actuator may compriseapplying a maximum current to the brake actuator, wherein furthestforward position may be dictated by the maximum current, wherein themaximum current allows the brake actuator to translate the ball nut inthe first direction to the furthest forward position.

In various embodiments, an aircraft may comprise a brake actuatorsystem. The brake actuator system may comprise a brake actuatorcomprising a ball screw, a ball nut coupled to the ball screw, and a ramcoupled to a ram end of the ball nut; a position sensor coupled to thebrake actuator; a processor in electronic communication with the brakeactuator and the position sensor; and/or a tangible, non-transitorymemory configured to communicate with the processor, the tangible,non-transitory memory having instructions stored thereon that, inresponse to execution by the processor, cause the processor to performoperations. The operations may comprise commanding the brake actuator totranslate the ball nut in a first direction toward a brake stack;detecting the ram reaching a furthest forward position; and/orcommanding the brake actuator to translate the ball nut in a seconddirection opposite the first direction for a total retraction distance.In various embodiments, the operations may further comprise determining,by the processor, a running clearance position of the ram in response totranslating the ball nut for the total retraction distance, wherein therunning clearance position may be positioned the total retractiondistance away in the second direction from the furthest forwardposition.

In various embodiments, the commanding the brake actuator to translatethe ball nut in a second direction for the total retraction distance maycomprise commanding, by the processor, the brake actuator to translatethe ball nut in the second direction for a predetermined retractiondistance from the furthest forward position; determining, by theprocessor, a zero torque position of the ram in response to translatingthe ball nut for the predetermined retraction distance, wherein the zerotorque position may be positioned the predetermined retraction distanceaway in the second direction from the furthest forward position; and/orcommanding, by the processor, the brake actuator to translate the ballnut in the second direction for a clearance distance from the zerotorque position. The predetermined retraction distance and the clearancedistance may collectively equal the total retraction distance.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure and are incorporated in, andconstitute a part of, this specification, illustrate variousembodiments, and together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 illustrates a cross section view of a portion of a wheel andbrake assembly, in accordance with various embodiments;

FIG. 2 illustrates a block diagram view of a brake actuator system, inaccordance with various embodiments;

FIG. 3A illustrates a cross section view of a portion of a brakeactuator with the brake actuator in the furthest forward position, inaccordance with various embodiments;

FIG. 3B illustrates a cross section view of a portion of a brakeactuator with the brake actuator in the zero torque position, inaccordance with various embodiments; and

FIG. 4 illustrates a method for determining a running clearance positionof a brake actuator system, in accordance with various embodiments.

DETAILED DESCRIPTION

All ranges may include the upper and lower values, and all ranges andratio limits disclosed herein may be combined. It is to be understoodthat unless specifically stated otherwise, references to “a,” “an,”and/or “the” may include one or more than one and that reference to anitem in the singular may also include the item in the plural.

The detailed description of various embodiments herein makes referenceto the accompanying drawings, which show various embodiments by way ofillustration. While these various embodiments are described insufficient detail to enable those skilled in the art to practice thedisclosure, it should be understood that other embodiments may berealized and that logical, chemical, and mechanical changes may be madewithout departing from the scope of the disclosure. Thus, the detaileddescription herein is presented for purposes of illustration only andnot of limitation. For example, the steps recited in any of the methodor process descriptions may be executed in any order and are notnecessarily limited to the order presented. Furthermore, any referenceto singular includes plural embodiments, and any reference to more thanone component or step may include a singular embodiment or step. Also,any reference to attached, fixed, connected, or the like may includepermanent, removable, temporary, partial, full, and/or any otherpossible attachment option. Additionally, any reference to withoutcontact (or similar phrases) may also include reduced contact or minimalcontact.

In the context of the present disclosure, systems and methods may findparticular use in connection with aircraft brake systems. However,various aspects of the disclosed embodiments may be adapted foroptimized performance with a variety of brake systems, includingautomobile brake systems and various other motor vehicle brake systems.As such, numerous applications of the present disclosure may berealized.

With reference to FIG. 1, a portion of a wheel and brake system 10 isillustrated, in accordance with various embodiments. Wheel and brakesystem 10 may comprise, for example, a brake assembly 11. In variousembodiments, brake assembly 11 may be coupled to an axle of a wheel 12.Brake assembly 11 may comprise brake stack 27 comprising rotors andstators that are compressed together by a brake actuator 36 to reducethe speed of a vehicle. In various embodiments, brake stack 27 maycomprise components that interface with the rotors, stators, and/or withthe wheel axle through torque tube 16.

Brake assembly 11 may further comprise, for example, one or more brakeactuators 36, which may be electromechanical. Brake actuators 36 may beconfigured such that in response to a command signal from a processor(e.g., in response to an operator depressing a brake pedal), brakeactuators 36 laterally compress brake stack 27 which, in turn, resistsrotation of wheel 12, thereby reducing the speed of the vehicle. Brakeactuator 36 may comprise, be coupled to, or otherwise operate a ballscrew and a pressure generating device, such as, for example, a ram 15.In response to a command signal (e.g., from a processor), a current maybe applied to brake actuator 36 causing the ball screw to rotate.Rotational motion of the ball screw may be transformed into linearmotion by a ball nut. The ball nut may comprise a ram end to which ram15 is coupled. Linear translation of the ball nut may cause ram 15 toapply lateral compression force on brake stack 27.

With reference to FIG. 2, a block diagram of a brake actuator system 200is illustrated, in accordance with various embodiments. Brake actuatorsystem 200 may comprise a brake actuator 210 coupled to a positionsensor 220. In various embodiments, position sensor 220 may be arotation sensor (e.g., a resolver). In various embodiments, positionsensor 220 may be coupled to brake actuator 210 and configured to detecta signal from which the number of rotations of the ball screw and/or thedistance translated by the ball nut may be calculated.

In various embodiments, brake actuator system 200 may comprise aprocessor 224. Processor 224 may be coupled to and/or in electroniccommunication with position sensor 220. In various embodiments,processor 224 may be comprised in position sensor 220. Processor 224 maybe configured to operate as a data acquisition and digital signalprocessing system. For example, processor 224 may receive data acquiredby position sensor 220. Such data may be processed, stored, and/oranalyzed by processor 224. In various embodiments, processor 224 maycomprise an analog to digital converter, which may be configured toreceive analog data acquired by position sensor 220 and convert it todigital data for processing by processor 224.

In various embodiments, brake actuator system 200 may further comprisean actuator controller 230 (e.g., an brake actuator controller(“EBAC”)). Actuator controller 230 may be coupled to and/or inelectronic communication with processor 224, brake actuator 210, and/orposition sensor 220. In various embodiments, actuator controller 230 maycomprise processor 224. After digital signal processing, actuatorcontroller 230 may receive data from processor 224, which may compriseposition information and/or commands for actuator controller 230 toexecute.

In various embodiments, processor 224 may be capable of bidirectionalcommunication with actuator controller 230. Bidirectional communicationbetween processor 224 and actuator controller 230 may, for example,allow for built-in testing to evaluate the health of actuator controller230, various sensors, and/or brake actuator 210, and/or to detect andcorrect error conditions, among other functions.

With reference to FIGS. 1, 3A, and 3B, a brake actuator 210 (an exampleof brake actuator 36 depicted in FIG. 1) is illustrated, in accordancewith various embodiments. In various embodiments, brake actuator 210 maycomprise a first end 310, a second end 311, a position sensor 220, abrake actuator housing 314, and an actuator seal 320. Actuator seal 320may comprise an annular ring disposed at the second end 311 of brakeactuator 210 and configured to at least partially surround a ball nut308. Actuator seal 320 may be configured to prevent and/or minimizeinfiltration of water, dirt, debris, contaminants, and/or the like intobrake actuator housing 314. In various embodiments, brake actuator 210may further comprise a ball screw 306 oriented about axis of rotation302, which extends in a linear direction from A to A′. Rotational motionof ball screw 306 is transformed into linear motion of ball nut 308along axis of rotation 302. Linear translation of ball nut 308translates ram 15 in a linear direction along axis of rotation 302 inand out of brake actuator housing 314 at second end 311 of brakeactuator 210. In various embodiments, ram 15 may be disposed on and/orcoupled to a ram end 312 of ball nut 308.

In various embodiments, position sensor 220 may be disposed on the firstend 310 of brake actuator 210. In various embodiments, at least aportion of position sensor 220 may be disposed between brake actuatorhousing 314 and ball screw 306. In various embodiments, at least aportion of position sensor 220 may be disposed in brake actuator 210,such that position sensor 220 is at least partially enclosed by brakeactuator housing 314. In various embodiments, at least a portion ofposition sensor 220 may be disposed on brake actuator 210, such thatposition sensor 220 is coupled to an exterior surface of brake actuator210, a housing thereof, and/or a component thereof. In variousembodiments, position sensor 220 may be coupled to and/or disposed onbrake actuator 210 in any suitable manner.

In various embodiments, brake actuator 210 may be in a fully retractedstate, wherein ram 15 has been translated as far as possible in adirection 367, or substantially as far as possible, in a lineardirection towards A along axis of rotation 302. The location of ram 15when brake actuator 210 is in a fully retracted state may be referred toherein as the fully retracted position 340. As used herein, a positionof ram 15 should be understood to be a location of ram 15 along axis ofrotation 302 relative to a fully retracted position 340. As used herein,translation of ram 15 in direction 369 towards A′ may be referred to asforward and/or positive translation, movement, and/or position;translation of ram 15 in direction 367 towards A may be referred to asbackward and/or negative translation, movement, and/or position. Stateddifferently, a first position of ram 15 axially closer to A′ than asecond position of ram 15 is to A′ may be described herein as exceedingthe second position of ram 15; a second position of ram 15 axiallycloser to A than a first position of ram 15 is to A may be describedherein as being less than the first position of ram 15. FIGS. 3A and 3Billustrate brake actuator 210 in extended states, wherein ram 15 hasbeen translated in direction 369 and the position of ram 15 exceedsfully retracted position 340.

In various embodiments, a brake actuator system comprising brakeactuator 210 may be configured to determine a zero torque position 360of brake actuator 210 and ram 15. In various embodiments, the zerotorque position 360 may comprise a position of ram 15, wherein the ram15 is not in contact or is in minimal contact with brake stack 27 andexerts no lateral compression force thereon. In other words, zero torqueposition 360 is the maximum position in direction 369 which ram 15 maybe disposed that does not exert compression force on brake stack 27.Therefore, in response to ram 15 being in zero torque position 360,brake stack 27 may be in a relaxed position 329, having no lateralcompression force between the discs of brake stack 27.

Positioning ram 15 in zero torque position 360 (e.g., while brakeactuator 210 is not in operation) may minimize delay in actuation of abrake system comprising brake actuator 210. For example, with combinedreference to FIGS. 1-3A, in response to the operator of a vehiclepressing a brake pedal (or otherwise commanding actuation of a brakesystem), brake actuator 210 of the vehicle's brake system may translateball nut 308 and ram 15 in direction 369 to compress brake stack 27 andslow the vehicle. However, if there is a gap between the position of ram15 and brake stack 27 before actuation of brake actuator 210, upon brakesystem actuation, there may be a delay in ram 15 reaching andcompressing brake stack 27, which may pose a safety risk to the vehicleand vehicle operator. Therefore, ram 15 being in zero torque position360 may cause little or no delay between brake system actuation andbrake stack 27 compression because slight movement of ram 15 indirection 369 will cause compression of brake stack 27 and slowing ofthe vehicle.

In various embodiments, placement of the ram 15 at the zero torqueposition 360 may cause drag and, consequently wear, on the brake stack27. Therefore, in various embodiments, a brake actuator systemcomprising brake actuator 210 may be configured to determine a runningclearance position 350 of brake actuator 210 and ram 15. Runningclearance position 350 may be a position further in direction 367 thanzero torque position 360. Running clearance position 350 may be aposition of ram 15 such that ram 15 does not contact brake stack at all27, which may help avoid drag and wear on brake stack 27 while brakeactuator is not in operation, as may happen if ram 15 is in zero torqueposition 360. However, running clearance position 350 may not createsignificant delay between brake actuator 210 actuation and compressionof brake stack 27, therefore avoiding the safety risks associated withsuch a delay.

In various embodiments, processor 224 may be configured to implementvarious logical operations in response to execution of instructions, forexample, instructions stored on a non-transitory, tangible,computer-readable medium. As used herein, the term “non-transitory” isto be understood to remove only propagating transitory signals per sefrom the claim scope and does not relinquish rights to all standardcomputer-readable media that are not only propagating transitory signalsper se. Stated another way, the meaning of the term “non-transitorycomputer-readable medium” and “non-transitory computer-readable storagemedium” should be construed to exclude only those types of transitorycomputer-readable media which were found in In Re Nuijten to falloutside the scope of patentable subject matter under 35 U.S.C. § 101. Invarious embodiments, the processor may be configured to implement smartalgorithms to calculate and/or determine a zero torque position 360and/or a running clearance position 350 of ram 15, discussed herein.

FIG. 4 depicts a method 400 for determining running clearance position350 of brake actuator 210, in accordance with various embodiments. Brakeactuator 210 may begin method 400 with ram 15 in any position (i.e., aninitial position) between fully retracted position 340 and a furthestforward position 365 (defined below). In various embodiments, withcombined reference to FIGS. 3A, 3B, and 4, processor 224 may commandbrake actuator 210 to translate ball nut 308 (step 402) in direction 369toward brake stack 27. In various embodiments, the commands fromprocessor 224 may be executed by actuator controller 230 (discussed inrelation to FIG. 2). To actuate brake actuator 210 to perform method400, a current may be applied to brake actuator 210. The current appliedmay be a maximum current applied to brake actuator 210, such that brakeactuator 210 may only apply a maximum pressure amount on brake stack 27that is proportional to the maximum current (i.e., the greater themaximum current, the greater the maximum pressure). The maximum currentmay be any suitable amount of current to allow any suitable maximumpressure. In response to a current being applied to brake actuator 210,the motor in brake actuator 210 may spin ball screw 306, translatingball nut 308 in direction 369.

Ball nut 308 may translate in direction 369, and ram 15 on ram end 312of ball nut 308 may contact brake stack 27. Ball nut 308 and ram 15 maycontinue to translate in direction 369, compressing brake stack 27. Inresponse to the maximum pressure applied by ram 15 against brake stack27 being achieved, the motor of brake actuator 210 may stall. The motormay stall because the maximum current applied to brake actuator 210 mayonly allow the maximum pressure to be applied by ram 15 against brakestack 27. Therefore, for ram 15 to apply more pressure than is allowedby the maximum current (i.e., pressure greater than the maximumpressure), additional current would have to be applied to brake actuator210. The position of ram 15 at the point in direction 369 at which themaximum pressure is applied to brake stack 27 (i.e., brake stack 27 maynot be compressed further in direction 369) is a furthest forwardposition 365 of ram 15 and brake actuator 210. Furthest forward position365 may be the point at which the maximum pressure applied in direction369 by ram 15 equals the pressure applied by spring force in brake stack27 in direction 367. Therefore, the brake discs in brake stack 27 may bein a compressed position 327 in response to ram 15 being in furthestforward position 365. Processor 224 may detect ram 15 reaching furthestforward position 365 (step 404). In various embodiments, processor 224may detect ram 15 reaching furthest forward position 365 by detectingthe motor of brake actuator 210 stalling.

In various embodiments, in response to ram 15 reaching furthest forwardposition 365 and processor 224 detecting the same, position sensor 220may detect the distance ram 15 and/or ball nut 308 translated from aninitial position to furthest forward position 365. As discussed above,position sensor 220 may be a resolver, wherein the resolver may provideposition data related to the number of rotations ball screw 306 made forram 15 to reach furthest forward position 365 from the initial positionof ram 15. Processor 224 may receive the information from positionsensor 220 (e.g., the resolver), and calculate and/or determine thedistance translated by ball nut 308 and/or ram 15. In variousembodiments, position sensor 220 may be a linear variable differentialtransformer (LVDT) and/or a linear encoder, wherein position sensor 220would detect the absolute positions of the initial position and furthestforward position 365 of ram 15. In response, processor 224 may receivethe position information from position sensor 220 and calculate thedistance between the initial position and furthest forward position 365of ram 15.

In response to processor 224 detecting ram 15 reaching furthest forwardposition 365, processor 224 may command brake actuator 210 to translateball nut 308 in direction 367 for a total retraction distance 354 (step406). Total retraction distance 354 may be the distance between furthestforward position 365 and running clearance position 350. In response,brake actuator 210 may translate ball nut 308 and ram 15 in direction367 the total retraction distance 354. In various embodiments, processor224 may determine running clearance position 350 (step 408) of theposition of ram 15 and/or ball nut 308 after having translated totalretraction distance 354 (i.e., running clearance position 350 may be theposition of ram 15 disposed the total retraction distance 354 indirection 367 away from furthest forward position 365). In variousembodiments, position sensor 220 may monitor ram 15 and/or ball nut 308position while brake actuator 210 translates ram 15 and ball nut 308 forthe total retraction distance 354. Processor 224, by receiving positioninformation from position sensor 220, may detect the completion of totalretraction distance 354 being translated by ram 15 and ball nut 308. Inresponse, in various embodiments, processor 224 may determine runningclearance position 360 (step 408) as the position of ram 15 and/or ballnut 308 after having translated total retraction distance 354. Processor224 may store the determined running clearance position 350. Processor224 may command brake actuator 210 to position ram 15 at runningclearance position 350 when brake actuator 210 is not in operation.

In various embodiments, processor 224 commanding brake actuator 210 totranslate ball nut 308 in direction 367 for a total retraction distance354 (step 406) may comprise commanding brake actuator 210 to translateball nut 308 in direction 367 the predetermined retraction distance 366(step 410). In response to processor 224 commanding brake actuator 210to translate ball nut 308 and ram 15 in direction 367 after reachingfurthest forward position 365, brake actuator 210 may translate ball nut208 and ram 15 in direction 367 for predetermined retraction distance366. Position sensor 220 may monitor ram 15 and/or ball nut 308 positionwhile brake actuator 210 translates ram 15 and ball nut 308 for thepredetermined retraction distance 366. Processor 224, by receivingposition information from position sensor 220, may detect the completionof predetermined retraction distance 366 being translated by ram 15 andball nut 308. In response, in various embodiments, processor 224 maydetermine zero torque position 360 (step 412) as the position of ram 15and/or ball nut 308 after having translated predetermined retractiondistance 366 (i.e., zero torque position 350 may be the position of ram15 disposed the predetermined retraction distance 366 in direction 367away from furthest forward position 365). Processor 224 may store thedetermined zero torque position 360. In various embodiments, processor224 may command that ram 15 be positioned at zero torque position 360when brake actuator 210 is not in operation.

Predetermined retraction distance 366 may be determined based on thespring coefficient (e.g., pounds per inch (kg/cm²) of displacement) ofbrake stack 27. For example, if the spring coefficient of brake stack 27is low (i.e., a loose spring force), predetermined retraction distance366 may be greater than if brake stack 27 has a high spring coefficient(i.e., a stiff spring force). In other words, brake stack 27 having alow spring coefficient results in brake stack 27 compressing more underthe maximum pressure, and having a furthest forward position 365 moreforward, than brake stack 27 having a high spring coefficient.Accordingly, predetermined retraction distance 366 is based on thespring coefficient of brake stack 27.

In various embodiments, processor 224 commanding brake actuator 210 totranslate ball nut 308 in direction 367 for a total retraction distance354 (step 406) may further comprise commanding brake actuator 210 totranslate ball nut 308 in direction 367 for a clearance distance 352(step 414), after determining zero torque position 360 and/or that ram15 had translated predetermined retraction distance 366. Clearancedistance 352 may be the distance of ram 15 in running clearance position350 in direction 367 from zero torque position 360, which may functionto prevent ram 15 from contacting brake stack 27 while brake actuator210 is not in operation. Clearance distance 352 may be any suitabledistance, such as 0.1 inch (0.254 centimeter).

In response to processor 224 commanding brake actuator 210 to translateball nut 308 and ram 15 clearance distance 352 in direction 367 afterreaching zero torque position 360, brake actuator 210 may translate ballnut 208 and ram 15 the clearance distance 352 in direction 367. Positionsensor 220 may monitor ram 15 and/or ball nut 308 position while brakeactuator 210 translates ram 15 and ball nut 308 the clearance distance352. Processor 224, by receiving position information from positionsensor 220, may detect the completion of clearance distance 352 beingtranslated by ram 15 and ball nut 308. In response, in variousembodiments, processor 224 may determine running clearance position 350(step 408) as the position of ram 15 and/or ball nut 308 after havingtranslated total retraction distance 354 (i.e., total retractiondistance 354 may be the predetermined retraction distance 366 plus theclearance distance 352 in direction 367 away from furthest forwardposition 365). Processor 224 may store the determined running clearanceposition 350. Processor 224 may command that ram 15 be positioned atrunning clearance position 350 when brake actuator 210 is not inoperation.

In various embodiments, a brake system may comprise alternative systemsand/or methods for determining running clearance position 350, such asby using a load cell to receive force feedback to determine the point atwhich there is no force on the ram from the brake stack and retractingfurther from that point to achieve running clearance position 350. Inthe event that alternative systems for determining running clearanceposition 350 (e.g., a position detection system) malfunction, processor224 may detect that such systems malfunctioning, and in response,processor 224 may utilize method 400 and brake actuator 210 to determinerunning clearance position 350. In various embodiments, brake actuatorsystem 200 (FIG. 2), comprising brake actuator 210, and method 400 maybe implemented as the primary method to determine running clearanceposition 350. Furthermore, systems and methods discussed herein may beutilized periodically throughout the life of a brake system and itsbrake discs to account for any changes in the zero torque positionresulting from brake disc wear.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”,“various embodiments”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A brake actuator system, comprising: a brakeactuator comprising a ball screw, a ball nut coupled to the ball screw,and a ram coupled to a ram end of the ball nut; a position sensorcoupled to the brake actuator configured to detect a number of rotationsof the ball screw in response to translating the ball nut in a lineardirection; a position detection system by which the brake actuatorsystem determines a running clearance position of at least one of theram and the ball nut; a processor in electronic communication with thebrake actuator and the position sensor; and a tangible, non-transitorymemory configured to communicate with the processor, the tangible,non-transitory memory having instructions stored thereon that, inresponse to execution by the processor, cause the processor to performoperations comprising: detecting, by the processor, a malfunction of theposition detection system; beginning with the ram in an unknown initialposition relative to a brake stack, commanding, by the processor, thebrake actuator to translate the ball nut and the ram in a firstdirection toward the brake stack in response to the detecting themalfunction of the position detection system; commanding provision of acurrent to the brake actuator, the current being associated with a knownmaximum force able to be applied by the ram to compress the brake stackand a known compression amount of the brake stack; detecting, by theprocessor, the ram reaching a furthest forward position; and commanding,by the processor, the brake actuator to translate the ball nut in asecond direction opposite the first direction for a total retractiondistance associated with the running clearance position in response tothe detecting the ram reaching the furthest forward position, such that,in response, the ram will be disposed at a running clearance positionrelative to the brake stack, wherein the running clearance position ispositioned the total retraction distance away in the second directionfrom the furthest forward position.
 2. The brake actuator system ofclaim 1, wherein the operations further comprise determining, by theprocessor, the running clearance position of the ram in response totranslating the ball nut for the total retraction distance.
 3. The brakeactuator system of claim 1, wherein the commanding the brake actuator totranslate the ball nut in the second direction for the total retractiondistance comprises: commanding, by the processor, the brake actuator totranslate the ball nut in the second direction for a predeterminedretraction distance from the furthest forward position; determining, bythe processor, a zero torque position of the ram in response totranslating the ball nut for the predetermined retraction distance,wherein the zero torque position is positioned the predeterminedretraction distance away in the second direction from the furthestforward position, wherein the zero torque position is the position ofthe ram closest to the brake stack without exerting a compression forceon the brake stack; and commanding, by the processor, the brake actuatorto translate the ball nut in the second direction for a clearancedistance from the zero torque position, wherein the predeterminedretraction distance and the clearance distance collectively equal thetotal retraction distance.
 4. The brake actuator system of claim 1,wherein the detecting the ram reaching the furthest forward positioncomprises detecting, by the processor, the brake actuator stalling inresponse to the brake actuator receiving insufficient current totranslate the ball nut further in the first direction.
 5. The brakeactuator system of claim 1, wherein the total retraction distance ismeasured by the position sensor.
 6. The brake actuator system of claim1, wherein the position sensor is a resolver.
 7. The brake actuatorsystem of claim 6, wherein the operations further comprise receiving, bythe processor, a signal from the resolver comprising distanceinformation; and determining, by the processor, a distance that the ballnut translated in the first direction from an initial position to reachthe furthest forward position.
 8. A method, comprising: detecting, by aprocessor, a malfunction of a position detection system by which a brakeactuator system determines a running clearance position of at least oneof a ram and a ball nut of a brake actuator; beginning with the ram inan unknown initial position relative to a brake stack; applying acurrent to the brake actuator in response to the detecting themalfunction of the position detection system, wherein the brake actuatorcomprises a ball screw, the ball nut coupled to the ball screw, and theram coupled to a ram end of the ball nut, wherein the current isassociated with a known maximum force able to be applied by the ram tocompress a brake stack and a known compression amount of the brakestack; commanding, by the processor, the brake actuator to translate aball nut coupled to the ball screw in a first direction toward the brakestack; detecting, by the processor, the ram coupled to the ram end ofthe ball nut reaching a furthest forward position in response to thecommanding the brake actuator to translate the ball nut; and commanding,by the processor, the brake actuator to translate the ball nut in asecond direction opposite the first direction for a total retractiondistance associated with the running clearance position in response tothe detecting ram reaching the furthest forward position, such that, inresponse, the ram will be disposed at a running clearance positionrelative to the brake stack, wherein the running clearance position ispositioned the total retraction distance away in the second directionfrom the furthest forward position.
 9. The method of claim 8, furthercomprising determining, by the processor, the running clearance positionof the ram in response to translating the ball nut for the totalretraction distance.
 10. The method of claim 8, wherein the commandingthe brake actuator to translate the ball nut in the second direction forthe total retraction distance comprises: commanding, by the processor,the brake actuator to translate the ball nut in the second direction fora predetermined retraction distance from the furthest forward position;determining, by the processor, a zero torque position of the ram inresponse to translating the ball nut for the predetermined retractiondistance, wherein the zero torque position is positioned thepredetermined retraction distance away in the second direction from thefurthest forward position, wherein the zero torque position is theposition of the ram closest to the brake stack without exerting acompression force on the brake stack; and commanding, by the processor,the brake actuator to translate the ball nut in the second direction fora clearance distance from the zero torque position, wherein thepredetermined retraction distance and the clearance distancecollectively equal the total retraction distance.
 11. The method ofclaim 8, wherein the detecting the ram reaching the furthest forwardposition comprises detecting, by the processor, the brake actuatorstalling in response to the brake actuator receiving insufficientcurrent to translate the ball nut further in the first direction. 12.The method of claim 8, further comprising receiving, by the processor, asignal from a position sensor comprising distance information; anddetermining, by the processor, a distance that the ball nut translatedin the first direction from the unknown initial position to reach thefurthest forward position.
 13. The method of claim 12, wherein theposition sensor is a resolver.
 14. An aircraft, comprising: a brakeactuator system, comprising: a brake actuator comprising a ball screw, aball nut coupled to the ball screw, and a ram coupled to a ram end ofthe ball nut; a position sensor coupled to the brake actuator configuredto detect a number of rotations of the ball screw in response totranslating the ball nut in a linear direction; a position detectionsystem by which the brake actuator system determines a running clearanceposition of at least one of the ram and the ball nut; a processor inelectronic communication with the brake actuator and the positionsensor; and a tangible, non-transitory memory configured to communicatewith the processor, the tangible, non-transitory memory havinginstructions stored thereon that, in response to execution by theprocessor, cause the processor to perform operations comprising:detecting, by the processor, a malfunction of the position detectionsystem; beginning with the ram in an unknown position relative to abrake stack, commanding, by the processor, the brake actuator totranslate the ball nut and the ram in a first direction toward the brakestack in response to the detecting the malfunction of the positiondetection system; commanding provision of a current to the brakeactuator, the current being associated with a known maximum force ableto be applied by the ram to compress the brake stack and a knowncompression amount of the brake stack; detecting, by the processor, theram reaching a furthest forward position; and commanding, by theprocessor, the brake actuator to translate the ball nut in a seconddirection opposite the first direction for a total retraction distanceassociated with the running clearance position in response to thedetecting the ram reaching the furthest forward position, such that, inresponse, the ram will be disposed at a running clearance positionrelative to the brake stack, wherein the running clearance position ispositioned the total retraction distance away in the second directionfrom the furthest forward position.
 15. The aircraft of claim 14,wherein the operations further comprise determining, by the processor,the running clearance position of the ram in response to translating theball nut for the total retraction distance.
 16. The aircraft of claim14, wherein the commanding the brake actuator to translate the ball nutin the second direction for the total retraction distance comprises:commanding, by the processor, the brake actuator to translate the ballnut in the second direction for a predetermined retraction distance fromthe furthest forward position; determining, by the processor, a zerotorque position of the ram in response to translating the ball nut forthe predetermined retraction distance, wherein the zero torque positionis positioned the predetermined retraction distance away in the seconddirection from the furthest forward position, wherein the zero torqueposition is the position of the ram closest to the brake stack withoutexerting a compression force on the brake stack; and commanding, by theprocessor, the brake actuator to translate the ball nut in the seconddirection for a clearance distance from the zero torque position,wherein the predetermined retraction distance and the clearance distancecollectively equal the total retraction distance.